ORDER VI 



CHELOXIA 



205 



covered with epidermal shields; plastral bones nine; no inframarginal shields. 

 Tertiary and Recent. 



The recent genus Chelys, Dumeril, is made by Baur the exclusive repre- 

 sentative of this family, and separate families are established for each of the 

 following : — Hydromedusa, Wagler (Recent) ; Chelodina, Fitz. (Pleistocene and 

 Recent) ; and Bhinemys, Wagler (Eocene to Recent). In Chelodina neural 

 bones are absent, and the external surface is more or less vermiculated. 



Family 4. Rhinemydidae. Baur. 



A slender or broad parieto-squamosal arch present ; posterior narial openings 

 bounded by maxillae, palatines, and vomer ; frontal paired ; nasals free ; premaxillae 

 distinct. Tertiary and Recent. 



Bhinemys, Wagler (Phrynops, Wagler ; Hydraspis, Bell). Eocene ; India ; 

 and Recent ; South America. Emydura, Bonap. Pleistocene and Recent. 

 Platemys, Wagler ; Elseya, Gray. Recent. 



Family 5. Pelomedusidae. Cope. 



Quadratojugal not in connection with parietal ; vomer rudimentary or absent. No 

 parietu-S'piamosal arch and no free nasals; prefrontals in contact. Second cervical 

 biconvex. Plastral bones eleven ; mesoplastra present. Tertiary and Recent. 



This family, as limited by Baur, includes only the recent Pelomedusa, 

 Wagler, and Sternothaerus, Bell. Cope regards the latter as the type of an 

 independent family, on account of the complete 

 mesoplastrals. The Podocnemididae differ from 

 the preceding genera in having the quadratojugal 

 connected with the parietals. Under this head are 

 included the follow- 

 Podocnemis, 

 (Fig. 305). 

 Eocene to Recent. 

 Peltocephalus, Dum. 

 and Bibr. ; Erymno- 

 chelys, Baur. Recent. 

 Daccochelys, Lyd. Eo- 

 cene ; and perhaps 

 Taphrosphys, Cope, 

 from the Upper Cre- 

 taceous of Xew Jersey 

 and Xew Zealand. 



The genus Bhino- 



chelys, Seeley (Fig. 306), from the Cambridge Greensand, known by well- 

 preserved skulls and various fragments, is of uncertain family position. 



Family 6. Plesiochelyidae. 



Skull with temporal fossae roofed. Shell usually thick, without mesoplastrals, am/ 

 with either a reduced or the full number of neurals and suprapygals ; only the pubis 

 uniting with the xiphiplastral ; entoplastral small; inframarginal shields at least 

 usually present. Sometimes a plastral vacuity. Phalangeals reduced. Upper Jura. 



ing: - 



Wagler 



Fig. 305. 



Podocnemis expansa, Wagler. 

 Recent ; Brazil. Visceral aspect of 

 posterior end of plastron, showing 

 places for attachment of pubes and 

 ischia, x, y (after Rntimeyer). 



Fig. ?,0G. 



RhinocTielys cantabrigiehsis, Lyd. 



Cambridge Greensand. Skull, l/l- 

 .1, < >rbit ; //', Frontal ; V, Nostril ; 

 na, Nasal; pa, Parietal; pmx, Pre- 

 niaxilla; pr/, Prefrontal ; /<(/", Post- 

 frontal (after Lydekker). 



